DUBAI, April 12 (Reuters) - The order books for Saudi Arabia’s debut U.S. dollar-denominated sukuk have reached about $25 billion, sources familiar with the matter said on Wednesday.

The dual-tranche sukuk, with maturities of five and 10 years, is set to be the largest ever Islamic bond, beating a $4 billion sukuk issued by Qatar in 2012. Books will close later on Wednesday, a document issued by one of the banks leading the deal showed.

Initial price guidance, released on Tuesday, put the senior unsecured Islamic bonds in the 115 bps over mid-swaps area for the five-year tranche and 155 bps over mid-swaps area for the 10-year tranche. (Reporting by Davide Barbuscia, editing by Louise Heavens)